1. Field of the invention
The present invention relates to a method for decomposing polyesters containing aromatic moieties, a method for reducing a fiber made of such polyesters, and microorganisms capable of decomposing fibers made of such polyesters.
2. Description of the Related Art
A law for recycling a container and wrapping was enforced in April, 1997 for reducing such wastes and the resulting environmental pollution, which has been attracting public attention. A grace period of 3 years is provided for a container and wrapping made of a plastic material, which will be under the law, necessitating a high cost for the recycling, from April, 2000. Polyethylene terephthalate, universally used for a container of soft drink and seasoning, also will be under the law. Manufacturers try to collect and recycle such container.
However, polyesters containing aromatic moieties, such as polyethylene terephtalate or polybutylene terephthalate, are finally treated by reclamation or burning-up. The burning-up process inevitably produces harmful wastes and the reclamation may produce floating wastes on water, both leading to further environmental pollution.
Therefore, a container or wrapping material made of a polymer containing aromatic moieties, and clothes and ornaments made of the polyester discharged in an apparel industry will require high costs for their recycling and should finally be treated by reclamation or burning-up. A solution for treating such materials has been demanded.
An object of the invention is to provide a method for treating a material or fiber made of a polyester containing aromatic moieties, with adverse effects on environment substantially reduced.
Another object of the invention is to apply such treating method to denier-reduction process of fiber.
The present invention provides a method for decomposing polyesters containing aromatic moieties, the method comprising:
contacting a microorganism having an activity of decomposing polyesters containing aromatic moieties with the polyester to decompose it.
The inventors succeeded in decomposing a polyester containing aromatic moieties by means of microorganisms for the first time in the globe. Although aliphatic polyesters have been known to be biodegradable, it has never been known that the polyesters containing aromatic moieties are susceptible to decomposition by microorganisms. As a result, the invention may decompose and degrade such aromatic polyesters without environmental pollution, then decomposition products with low molecular weights may be returned into a substance-recycling system in natural environment.
The inventive method for decomposing polyesters containing aromatic moieties may be applied to a container, a wrapping material, as well as a fiber and cloth, each made of such polyesters. When the wastes containing the polyesters are subjected to composts, microorganisms included in the composts rapidly decompose the polyesters into nontoxic substances. Alternatively, when the wastes containing the polyesters are reclaimed, microorganisms may be included in wastes to decompose the polyesters. Such polyester wastes, contained in the composts or the reclaimed wastes, may be partly or wholly decomposed.
An effective treatment has not been found yet to treat so called a pet-bottle (a bottle made of polyethylene terephthalate). The invention provides a method for treating such bottle without leaving further wastes in natural environment.
The other treating methods, such as reclamation and burning-up, may produce harmful substances. The inventive microorganisms capable of decomposing the polyesters may survive for a long time, even when utilizing the polyesters as a sole carbon source, thereby probably alleviating the possibility of producing harmful substances.
The inventors also succeeded in applying the inventive decomposition method for denier reduction process of the surface of fibers made of polyesters containing aromatic moieties. The inventive reducing method produces no decomposition residue, which has been inevitably produced in the previous caustic (denier) reduction method of a fiber, thereby providing technique suitable for environment. The inventive reduction method is also useful for obtaining a fiber with better fitting and appearance. For example, a cotton fiber has been treated to improve its fitting and appearance by means of cellulase derived from microorganisms. The inventive denier reduction method may also produce a fiber and cloth made of the polyesters with improved fitting and appearance. Moreover, the thus obtained fiber has small depressions, hollows and ditches or grooves on the surface formed during the reduction process, thus facilitating its dyeing.
The inventors have confirmed the activity of decomposing a polyester containing aromatic moieties, in the following microorganisms.
(1) Trichosporon FERM BP-6445
(2) Arthrobacter FERM BP-6444
A polyester containing an aromatic moiety is a polyester produced by polymerizing monomers, at least one of the monomers being an aromatic compound. Such polyester is not particularly limited. However, such polyester may preferably be a polyalkylene phthalate, isophthalate or terephthalate, more preferably be polyethylene terephthalate, polypropylene terephthalate, or polybutylene terephthalate, and most preferably be polyethylene terephthalate or polybutylene terephthalate. The polyester may be a homopolymer of an aromatic compound, or a copolymer of aromatic compounds, or a copolymer of an aromatic compound and an aliphatic compound. The aromatic compound is not limited, and preferably be alkylene terephthalate such as ethylene terephthalate, propylene terephthalate and butylene terephthalate.
These and other objects, features and advantages of the invention will be appreciated upon reading the following description of the invention when taken in conjunction with the attached drawings, with the understanding that some modifications, variations and changes of the same could be made by the skilled person in the art.